Make different methods of LBP more readable in Cython code

skimage/feature/_texture.pyx

@@ -80,7 +80,7 @@ cdef inline int _bit_rotate_right(int value, int length):
 
 
 def _local_binary_pattern(np.ndarray[double, ndim=2] image,
-                          int P, float R, int method=0):
+                          int P, float R, char method='D'):
     # texture weights
     cdef np.ndarray[int, ndim=1] weights = 2 ** np.arange(P, dtype=np.int32)
     # local position of texture elements
@@ -116,7 +116,7 @@ def _local_binary_pattern(np.ndarray[double, ndim=2] image,
             lbp = 0
 
             # if method == 'uniform' or method == 'var':
-            if method == 2 or method == 3:
+            if method == 'U' or method == 'V':
                 # determine number of 0 - 1 changes
                 changes = 0
                 for i in range(P - 1):
@@ -128,7 +128,7 @@ def _local_binary_pattern(np.ndarray[double, ndim=2] image,
                 else:
                     lbp = P + 1
 
-                if method == 3:
+                if method == 'V':
                     var = np.var(texture)
                     if var != 0:
                         lbp /= var
@@ -139,7 +139,8 @@ def _local_binary_pattern(np.ndarray[double, ndim=2] image,
                 for i in range(P):
                     lbp += signed_texture[i] * weights[i]
 
-                if method == 1:
+                # method == 'ror'
+                if method == 'R':
                     # shift LBP P times to the right and get minimum value
                     rotation_chain[0] = <int>lbp
                     for i in range(1, P):

skimage/feature/texture.py

@@ -235,14 +235,14 @@ def local_binary_pattern(image, P, R, method='default'):
     Parameters
     ----------
     image : (N, M) array
-        graylevel image
+        Graylevel image.
     P : int
-        number of circularly symmetric neighbour set points (quantization of the
-        angular space)
+        Number of circularly symmetric neighbour set points (quantization of the
+        angular space).
     R : float
-        radius of circle (spatial resolution of the operator)
-    method : {'default', 'ror', 'uniform', 'var'}
-        method to determine the pattern::
+        Radius of circle (spatial resolution of the operator).
+    method : {'D', 'R', 'U', 'V'}
+        Method to determine the pattern::
         * 'default': original local binary pattern which is gray scale but not
             rotation invariant.
         * 'ror': extension of default implementation which is gray scale and
@@ -256,7 +256,7 @@ def local_binary_pattern(image, P, R, method='default'):
     Returns
     -------
     output : (N, M) array
-        LBP image
+        LBP image.
 
     References
     ----------
@@ -268,10 +268,10 @@ def local_binary_pattern(image, P, R, method='default'):
     """
 
     methods = {
-        'default': 0,
-        'ror': 1,
-        'uniform': 2,
-        'var': 3
+        'default': ord('D'),
+        'ror': ord('R'),
+        'uniform': ord('U'),
+        'var': ord('V')
     }
     image = np.array(image, dtype='double', copy=True)
     output = _local_binary_pattern(image, P, R, methods[method.lower()])